Let us check out the verb ‘send‘ in different phrases.

send for means to summon or to request the coming of
The boss sent for me and asked for an explanation.
Send for the doctor if her condition deteriorates further.

send in means to get something delivered or dispatched
You must send in your résumé at the earliest.
Send in your entries for this contest to the given address.

send off means to dismiss or cause to depart
He was sent off to the principal’s office after he misbehaved in the class.
I was sent off to a hostel when I was eight.

send out means to distribute or to send on the way
The final shipment was sent out last week.
We sent out the remaining goods last Friday.