How to get block height

Hi, is there a tool or API to query the block status like current block height and highest block height?

as well as

I think current block height is burn_block_height.
What is exit_at_block_height mean?

@ark930 exit_at_block_height: The testnet will stop at that block height

burn_block_height: Block height on burn chain (=bitcoin chain)
stacks_tip_height: Block height on stx chain