There are several types of bottom brackets for bicycles, including:
Threaded bottom brackets: These are the most common type of bottom bracket and are found on most traditional road and mountain bikes. They screw into the frame and use threaded cups to secure the bearings.
Press-fit bottom brackets: These are becoming more common on modern road and mountain bikes. They press into the frame instead of being screwed in and use cups to secure the bearings.
External bottom brackets: These are a type of threaded bottom bracket that have the bearings located outside of the frame. They are typically found on newer road and mountain bikes and are easier to service than internal bottom brackets.
Internal bottom brackets: These are a type of threaded bottom bracket that have the bearings located inside the frame. They are becoming less common as external bottom brackets become more popular.
Tapered bottom brackets: These are a type of bottom bracket where the spindle is tapered towards the ends. They are typically used on high-end road and mountain bikes and offer improved stiffness and durability.
It's important to know what type of bottom bracket your bike has when replacing or servicing it to ensure you use the correct tools and parts.