Each person gets the same fixed number of points, and they can allocate the points to each candidate however they prefer, as long as the sum of points allocated equals the number of points given. The person with the most points wins.
This system is called cumulative voting.
It is occasionally used on municipal level elections and also sees some use in workplace voting.
Ballots for this usually look like this, with one column for each vote:
This example ballot is from a district parliament election in the city of Hamburg, Germany.