The impersonal expression "c'est" changes to "ce sont" when followed by a plural noun. "Ce" is a pronoun in the phrase "c'est" / "ce sont".
"Ce" does not change to "ces" (not: ces sont).
"Ces" is not a pronoun. It is an adjective that is used only when it is followed by a plural noun.
well there is a difference between les and des. les means "the" and try to think of des as either "some" or you can also just think of it as a word that needs to be there if not using "les" ("the"). in this example, "these are dresses", the word "the" is not in there, which is why you should use "des". as for the context of the sentence, think of it as saying, "here are some dresses" (in general) rather than "here are THE dresses" (for example the dresses you've been looking for or the dresses you're referring to in specific)... nothing to do with gender btw.
Well, now be careful. In English there are two times that we don't put an article with a plural noun. When we mean "some", but this word is optional and that is the case for this sentence.
The other time is for a generalization, for example: "People eat food." In French, they use the definite article for a generalization, so it would be "Les gens mangent la nourriture."
No, "elles" is used for any feminine plural noun, whether a living being or an object. It can refer to "femmes", "voitures" (cars), whatever, as long as it's grammatically feminine plural.
The reason this is "ce sont" and not "elles sont" is because "il/elle est" and "ils/elles sont" change to "c'est" and "ce sont" before a modified noun, that is, a noun preceded by a modifier. A modifier can be:
- an article: un, une, des, le, la, l', les
- a number: un, deux...
- a possessive adjective: mon, ton, son, ma, ta, sa, notre, votre, leur, mes, tes, ses, nos, vos, leurs
- a demonstrative adjective: ce, cet, cette, ces
"il/elle est" + adjective stays "il/elle est" + adjective.
These articles go into more detail and are worth a read.
Also, the Tips and Notes for the Gallicism skill (click the lightbulb icon when you open the skill) give more information.