Querying through the posts can be useful for creating special container pages. Returning the posts you require is only a matter of using the right attributes.
A query in WordPress looks like a series of GET variables:
This will return all posts that are in category 7, and will order them alphabetically.
WordPress offers also other functions that help query for the right posts:
have_posts(); – boolean, determines if the query was successful
the_post(); – focuses on one post from the iteration, allows different operations
get_the_category(); – returns the category of the post
get_the_title(); – returns the title of the focused post
More example under: https://codex.wordpress.org/Function_Reference/