E.g. I have account A with lots of CPU, and account B with not so much of it.
Normally I'd sign transaction with B, and push with B, so spend B's CPU.
Is there any way to send B's transaction with A's CPU?
If the trx allows, you could sign the trx with B's key, thus B would be charged for something that benefits A.
Alternatively you can stake to B from A the EOS in CPU/NET. More on staking here https://developers.eos.io/manuals/eosio.contracts/v1.9/key-concepts/stake