In French, what does agreement mean again?

Cause for example I put down this:

Ils ont marches sur l'Avenue Champs-Elysees.

But there shouldnt be an S after marche because theres no agreement with avoir.

Could I please know what agreement means again?

marché (passé composé with avoir only has the past participle agree with a preceding direct object.) There is none here.......Eysées

Verbs conjugated with être have the past participle agree with the subject...
Ils sont allés (for girls = allées)
Elle est morte

With adjectives, agreement means the adjective has the same number (singular/plural) and gender (masculine/feminine) as the noun(s) modified
la maison blanche
les livres lourds (heavy)

With verbs, there is agreement of the proper ending, depending upon the subject
je finis
ils finissent

Above are 4 types of agreement.

Sra (aka Mme)

Okay so would agreement just be the endings?

I suppose you "could" say that! I just never thought of it in those terms!

Sra (aka Mme)

P.S. There are so many definitions for the word "agreement" but here's what I found when it refers to grammar:
correspondence in grammatical case, number, gender, person, etc., between syntactically connected words.

I like your definition better, thanks=)

And just if you'd like to know, the book I have is called C'est A toi! And it it Level 2.

In French grammar, agreement refers to a phenomenon where certain words, such as nouns, adjectives, and past participles, change their form to match the gender and number of the noun or pronoun they are modifying. In the sentence you provided, "Ils ont marches sur l'Avenue Champs-Elysees," you are correct that there is no agreement between the auxiliary verb "ont" and the past participle "marches."

In this case, "Ils" is the plural subject pronoun, whereas "marches" is the plural past participle of the verb "marcher." However, because the auxiliary verb "avoir" does not require agreement with the subject in compound tenses, you do not need to add an "s" to "marches."

To know when to apply agreement, it is important to consider the type of verb used (such as "avoir" or "être"), the tense being used, and the subject in terms of number and gender.