Learn English – ny difference between “invite to” and “invite for”

Dinner is considered to be the "main" or largest meal of the day. Whether it takes place at noon or in the evening is mostly a cultural thing. For instance, many people who grew up in the American South and/or on farms traditionally ate larger meals at noontime to give them the strength to keep working through the afternoon.

Supper is more specifically a lighter evening meal. Rooted in the word "to sup", it comes, again, from farming traditions — many farming families would have a pot of soup cooking throughout the day, and would eat it in the evening — specifically, they would "sup" the soup.

Lunch is almost the midday equivalent of supper — it's also a lighter and less formal meal than Dinner, but is used specifically when referring to a midday meal. So whether you use lunch/dinner or dinner/supper is heavily determined by when your culture traditionally has its largest meal.

Much Later Edit: I happened across this article discussing the agricultural roots of midday dinner and evening supper, just to add a bit more to the conversation.

Yes. Continuous means from some start to some end without break:

The water flowed continuously over the dam.

whereas continual means occurring repeatedly at intervals over a time span:

I continually lose at poker.

I should also mention that continual is often substituted for continuous, and would be correct in most contexts, however the converse is not generally true. That is to say,

The water flowed continually over the dam.

is okay, but you would (hopefully) not mean

I continuously lose at poker.

since that would imply that all you do all day long is play poker and lose.