How much does BTC charge per transaction?

Could you please clarify for me the cost associated with each Bitcoin (BTC) transaction? Is there a standard fee that is applied universally, or does the charge vary based on factors such as the size of the transaction, the current network congestion, and perhaps even the miner's individual preferences? Additionally, are there any hidden costs or fees that a user should be aware of when initiating a BTC transaction? Understanding these aspects would be crucial for me to make informed decisions when engaging in Bitcoin transactions.