Question

What’s the difference between 1. Normal put and protective put 2. Normal call and covered call

Answer 1

1.
Normal put also called naked put involves buying put without holding any position in the underlying.
Protective put involves buying put and also holding a long position in the underlying.

Profit from protective put is given as
St-S0+MAX(X-St,0)-P

If X>St: X-S0-P
If X<St: St-S0-P

Profit from normal put is given as
MAX(X-St,0)-P

If X>St: X-St-P
If X<St: -P

2.
Normal call also called naked call involves buying a call without holding any position in the underlying.
Covered Call involves selling a call and holding a long position in the underlying.

Profit from covered call is given as
St-S0-MAX(St-X,0)+C

If X<St: X-S0+C
If X>St: St-S0+C

Profit from normal call is given as
MAX(St-X,0)-C

If X<St: St-X-C
If X>St: -C