encontrar vs buscar
Buscar is the searching. Encontrar is the finding. One is the journey, one is the result.
buscar
To look for, to search — the process of seeking. Crucially: no 'for' needed in Spanish.
Estoy buscando mis llaves.
I'm looking for my keys.
No 'por' or 'para' needed. Buscar already means 'look for' — buscar por is wrong.
Busca trabajo desde hace meses.
He's been looking for work for months.
The search is ongoing. He hasn't found it yet.
¿Me puedes buscar un vuelo?
Can you look up a flight for me?
Search in the digital sense too. Completely natural.
encontrar
To find, or to find (in the sense of consider/think) — the discovery.
Al final encontré las llaves.
I finally found the keys.
The search (buscar) ended. This is the result.
Encuentro este libro muy interesante.
I find this book really interesting.
Encontrar = to find in the opinion sense. Very common. Like French 'trouver.'
Nos encontramos por casualidad.
We ran into each other by chance.
Encontrarse = to meet/run into someone. Reflexive use.
Tricky bit
English speakers say 'buscar por' because 'look for' has 'for.' Spanish doesn't need it. And 'encontrar' for opinions ('lo encuentro aburrido') is something many learners miss — they use 'pensar' instead, which also works but is less idiomatic.