Support is price level below the current market price at which buying interest should be able to overcome selling pressure and thus keep the price from going any lower.
Resistance is Price level above the current market price, at which selling pressure should be strong enough to overcome buying pressure and thus keep the price from going any higher.
Support and resistance analysis is an important part of trends as it can be used to make trading decisions and identify when a trend is reversing
When price drops to a support level, it will go back up
When price rises to a resistance level, it will go back down
Support and resistance levels both test and confirm trends and need to be monitored by anyone using technical analysis
Check Technical Analysis course for better understanding.