Bottom
Brackets
CeramicSpeed
BB86 SRAM DUB Road Bottom Bracket
CeramicSpeed
BSA Campagnolo UT 25mm Bottom Bracket (Coated)
Hope Technology
MTB Stainless Steel 30mm Bottom Bracket
Problem Solvers
Bushnell Eccentric Bottom Bracket - Lightweight (68mm)
All bikes have bottom brackets, including road bikes, e-bikes, mountain bikes, hybrid bikes and gravel bikes. The bottom bracket of the bike connects the crankset of the bike to the frame - meaning that the crankset can rotate, without the entire frame rotating!
Bottom brackets will typically last for thousands of miles, which can be a couple of years for riders - although bottom brackets on mountain bikes may need replacing sooner, with ingress of mud & grime from the trails - which can be negated by a strict cleaning regimen. The biggest giveaway to a bottom bracket that needs replacing, is a wobbling crank or excessive noise from the bottom bracket.
In some cases, a noisy bottom bracket may not need replacing - it may just need the bearings replacing or greasing.