QUICK ANSWER
"La tilde" is a form of "tilde", a noun which is often translated as "accent". "El" is a form of "el", a definite article which is often translated as "the". Learn more about the difference between "la tilde" and "el" below.
la tilde(
teel
-
deh
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
a. accent
Olvidaste ponerle la tilde a la primera vocal en "túnel".You forgot to put the accent on the first vowel of "túnel".
2. (diacritic)
a. tilde
Las letras "ñ" y "n" en español se diferencian por la tilde.The letters "ñ" and "n" in Spanish are distinguished by the presence or absence of the tilde.
el(
ehl
)A definite article is a word that identifies a noun as specific or known to the speaker (e.g., the girl).