The technique which is a card-based estimation based on a general agreement is known as scrum poker or planning poker. Some features of it are:-
The first step is to story of the agile user is read by the customer or owner. Then the estimator understands the features.
There are different planning cards with a different number for each estimator. The different numbers are the story points.
Based on the estimation which is done by discussing features, the estimator will select a card.
When a common value is selected then it is considered to be an estimate otherwise there is a discussion on maximum and minimum estimation.
Until a general agreement is reached this process is repeated.