aprender vs enseñar
Learn vs teach — and enseñar also means 'show'. Mixing them up is one of the few errors that flips who's doing what.
aprender
To learn, to pick up a skill or knowledge.
Aprendí inglés en Londres.
I learned English in London.
Acquiring a language or subject.
Aprendí a nadar de niño.
I learned to swim as a child.
Aprender a + infinitive = to learn how to.
Aprende muy rápido.
He learns very fast.
General ability.
enseñar
To teach — and to show something to someone.
Enseña matemáticas en un instituto.
She teaches maths at a secondary school.
Teaching a subject. 'Dar clase' is a common alternative.
Me enseñó a conducir.
He taught me to drive.
Enseñar a + person + a + infinitive.
Enséñame la foto.
Show me the photo.
Enseñar also means show, even without any teaching going on. Mostrar is more formal.
Tricky bit
'Me enseñó español' = he taught me Spanish. 'Aprendí español con él' = I learned Spanish with him. The subject changes depending on the verb, so mixing them swaps teacher and student.