Bandwidth Rate Limiting for Fee-less Operations

Because the witnesses are paid entirely through the generation of new tokens, there is no need
to charge users a fee for powering the blockchain. The only reason to charge a fee would be
as a deterrent to prevent users from completing an unreasonable amount of transactions, which
could potentially impact the performance of the blockchain.
In order to place reasonable limits on the system use, each user is given a limited bandwidth.
Whenever users perform blockchain operations such as token transfers, posting content, and
voting, it uses up a portion of their bandwidth. If a user exceeds their bandwidth allowance, they
must wait to perform additional actions until their bandwidth recharges.

I can't understand about the part above...