Note that all of these are operators, not commands:

• && — this is a logical AND and is used to chain multiple commands; commands to the right of the operator are executed if the command to the left succeeds
• || — this is the logical OR and is used to chain multiple commands; commands to the right of the operator are executed if the command to the left fails
• / — not a command, not an operator. Period.
• ; — this is a command delineator or separator; you use it to separate commands where you want all of them to execute
• {} (and () ) — operators that do a bunch of stuff; I tend to use () for grouping commands into one “unit”, and use {} for its command line expansions (a bit complicated to go into right here)