Please note that this is not based on any cited source but on my own observations.
Colloquia and seminars both happen in an academic setting. At my university we have a weekly physics colloquium that — in general — is geared to a well educated, but not specialized audience. (I.e., a particle physicist will present a topic on a fairly advanced level, but so that, say, a condensed matter physicist will still be able to understand). In general they seem to be more "populist" and less technical, covering popular topics in physics (quantum information, graphene) and in the news (global warming, nuclear weapons/power) but from the perspective of a scientist.
A seminar on the other hand, in an academic setting, is a much more specialized meeting, also with a formal academic presentation. For instance, there are weekly seminar meeting for the Atomic, Particle, String Theory, Condensed Matter, and Astrophysics groups. There is also an invited speaker, but the audience is much more technically versed and the topics tend to be much more technical or specific to the field. Generally someone from outside the field will have trouble understanding a seminar presentation.
In a grand sense the two words are equivalent, but a colloquium, as pointed out, is literally a "conversation" and in general has a connotation of being more broad, more accessible, or on a more popular topic.
I think command / invitation is a dichotomy much the same as desirability / probability as recently explored by this question.
IMHO you will not find 'rules' unambiguously telling you how distinguish between modes of command, invitation, permission, expectation, etc. because speakers frequently wish to blur those distinctions.
At one extreme is simply the wish to avoid giving offense, by couching a command as an invitation. At the other is the domineering tactic of a powerful person assuming that his slightest indication in favour of some particular outcome should be taken by his underlings as a direct command to progress things in that direction.
Human interaction is the primary function of language, and the dominant / submissive juxtaposition is one of the key elements of that interaction. All of us 'bend' language in this area from time to time to suit our own agenda. And over time, all of us unconciously connive at making sure the language is easily bent in this area.
In short - if you want to identify structural differences between a command and an invitation, you'd do better to ask a psychologist rather than a grammarian or linguist.
Best Answer
A fund is an existing collection of money. Funding is the source of that collection. In other words, funding is the money coming into the fund. They can often be used interchangeably, but they do mean slightly different things.