There are two types of tender security: participation and performance.
Participation security is the guarantee that, if won, the contractor will not merge.
In 95% of cases, it is paid in live money, which is frozen for about 2-4 weeks while the purchase is underway. As soon as the winner is determined (you or not - it does not matter), they are returned to your account.
Enforcement is basically a penalty if you withdraw from the contract (either by yourself or because you failed). In 99% of cases it is a bank guarantee, for money - about 0.3-0.5% of the total purchase price. Accordingly, if you failed to cope with the contract, the bank will collect from you the amount of this security. And levy - everything clearly works.
Of course, the security can be paid in live money, but who needs to freeze a few hundred thousand rubles for months or years?