The symbol for resistance is R, it is measured in ohms \((\Omega )\). The symbol for current is I, it is measured in amperes \((A)\).

All conductors show some opposition to electric current. This opposition to current is called resistance. A good conductor has low resistance. A poor conductor, or insulator, has high resistance.

I'll try to explain all this as simply as possible since the technical answer of "ohm is the unit of electrical resistance" isn't particularly helpful for anyone not currently in high school science.