your bitaxe takes a block template and nonce and hashes it. it keeps changing the nonce and hashing, looking for a hash smaller than a specific number (often described as leading with a specific number of 0s).
difficulty is an inverse representation of how small your hash is. the higher the difficulty the lower the hash.
I dont want to get in to the math of how difficulty is calculated based on how small the hash is but the important thing to know is:
if you hash a block with a difficulty higher than the network target difficulty then you have successfully found a block.
current network difficulty is about 127 T.