EQ: What is a definite article and
how do I use one correctly in
Spanish?

A definite article is used before a noun to know the identity of a noun.

Examples in Spanish: el, ella, nosotros, nosotras, ellos, ellas

To correctly use the articles defined in Spanish, just remember this:

If you are talking about something in masculine, it must have the letter "o" and "e"

If you are talking about something in the feminine it must have the letter "a"

Extra:

The indefinite article is used before a noun which is when its identity is unknown.

Examples in Spanish: un, lo

If you are talking about something that is not feminine or masculine, that is, something indefinite, remember that it can never be placed before nouns, because it does not have the function of determining the gender of words.