Support and resistance are important points or levels, that are used by the investor or trader to trade in a security or share price.
Support is the level where demand is strong enough to prevent the stock from falling further. Each time the price reaches the support level, buyers buy shares at that price. In support level buyers are more active than seller. So, it is difficult break that level. If the support level break, a new support level will establish at another price.
Resistance is the level where supply is strong enough to prevent the stock from moving higher. Each time the price reaches the resistance level, sellers sell shares at that price. In resistance level sellers are more active than buyers. So, it becomes difficult break that level. If the resistance level break, the share price will move to a higher level and a new resistance level will establish at another price.