I basically agree with SoltBegins, but let me state it a different way.
To "give effect to" something is to make it work, to make it carry out its desired intent.
To "effect" something (as a verb) is to bring it into existence or make it happen.
So if you said, "Mr Smith effected an agreement between the parties", that would mean that Smith managed to convince the parties to come to some compromise. Like, he convinced them that they should each pay half the cost. If you said, "Mr Smith gave effect to the agreement between the parties", that would mean that he did something to make the agreement actually happen, like he collected the money from each of them.
Addendum
To try to answer your question:
By "make it happen" here I mean something along the lines of "bring it into existence". Maybe it would have been more clear if I'd just left it at "bring it into existence".
"Give effect to" specifically means to cause something that previously existed only as an idea or on paper to actually happen. We routinely talk about "giving effect to a contract" or "giving effect to the new law".
To "effect" simply means to cause, or cause to exist. Sometimes, often, causing something to exist and making it happen are the same thing. When we say "Smith effected X" we often mean that he both caused it to exist and caused it to produce the desired outcome. If, for example, you say "I effected an update to the document", making the update exist and making it actually change the document are probably a single event, you can't separate them out. So in a given case,
whether "to effect X" means to create a concept that is not yet actually happening in the real world,
or if it means both to create the concept and to really make it happen, depends on the context.
In the case of an agreement, if all the parties are truly willing it might be that once the agreement is made, they all go off and do whatever, and no one thinks of a separate step of giving effect to the agreement. It just depends on context.
You can say asking for permission and it means the same as asking permission. You can also say asking for advice as well as asking advice. Whether you use the preposition "for" or not, the phrases mean the same thing.
This is because "ask" is either transitive or intransitive. You can see the definition of "ask" here:
http://www.oxfordlearnersdictionaries.com/us/definition/english/ask_1
Here is a web page that describes transitive verbs in greater detail:
http://www.chompchomp.com/terms/transitiveverb.htm
Basically, a transitive verb requires an object for the sentence, whereas an intransitive verb links permission to ask through the use of a preposition such as for. When a verb is defined as either transitive or intransitive, then it's up to the writer to decide whether to use a preposition or not. Asking for permission and asking permission have more or less the same meaning, but there may be instances when using the preposition could make the sentence clearer to the reader.
Best Answer
They are pretty close in meaning, actually! Here are the rules:
Use
to
when you want to express that the result of the verb will affect or in some way be done /to/ the following noun.Use
for
when you want to express that the action is being done for the sake of or on behalf of the following noun, or when the preceding object is intended to be given, to affect, or be caused or expected by the following noun.These can overlap a lot, so sometimes either one is good!
What is more of a problem above is confusing
ensure
andinsure
:Use
ensure
to indicate a process of making an uncertain event more certain.Use
insure
or when you mean taking a course of action that makes the negative effects of a contingency less costly or bad, or when you are speaking of an insurance (financial product, or other object which insures in the first sense).^ This means that if we do not pollute less, all of humanity will be harmed as a result.
^ This means that should do so so that all of humanity will be harmed minimally.
^ This means that on behalf of, or for the sake of all of humanity, we need to make certain that we do the least harm. The object of the harm is not specified, but we understand it to also be
humanity
.It could also mean roughly the same as the above example - because the
minimum amount of harm
is intendedfor all of humanity
by the recommended action.If you were to say:
^ This would not be incorrect grammar, but it is less common use, and may sound awkward. Although most listeners would understand what you meant, it can sound like
all of humanity
wants the speaker to cause harm to some unspecified thing, and the speaker does not want to fulfill their wish.It could also have the second sense of
for
above, so it isn't "wrong" and you may find some occurrences wherefor
is used like this. But you should likely prefer to useto
here instead.