Hi Jonathan!
"Reunir" means "to gather" and "encontrar" means "to find".
Nevertheless, when we talk about people and we use the reflexive form, "reunirse" means "to get together".
"Encontrarse" (encontrarse con alguien) can mean the same in that case, but it usually means "to run into someone" (to find someone unexpectedly)
We can say:
"Nos reuniremos allí a las 8" or
"Nos encontraremos allí a las 8"
(We'll get together there at 8)
"Ayer me encontré con Juan"
"I bumped into John yesterday"
I hope this helps.
Have q great day.
^_^