A 'combination' wrench has a flat end and a round end. The round end is used to release very tight nuts (for instance the nuts the hold springs or shocks on cars) -Once they are loosened it's easier to turn them with the flat end.
A combination wrench has an open end on one end and a box end on the other. The 18mm designates what size nut/bolt the wrench fits.
Yes, a wrench is easy to use.
What wrench?
You can purchase a combination wrench set online from stores such as Sears. Alternatively, you can purchase this item from retailers such as Amazon and Grainger.
Usually I use a crescent, or adjustable wrench.
Like a regular wrench
A strap wrench Or an inside wrench
If you mean a wrench to use in missions, then the wrench is built right into your spy phone!
lug wrench
Yes, you can use a torque wrench in both directions.
You use a 16 mm or 5/8 wrench.
I would use a 13 mm wrench. If you don't have one you should get one ! This and 10mm are the two most common metric sizes in bolts etc. -For now you can also use a 17/32 wrench or a crescent wrench.