Anyone know what’s the meaning behind some weird car plates I’ve been seeing?

This year, I've seen many of those vanity plates here in Houston but there are some that have caught my eye and I'm just curious on what they mean. They are black plates and they all start with a letter, usually "B," then a few numbers, then they end with "K." Now I don't know about anyone else but if I was to buy a vanity plate and pay almost 4 times as a regular plate, I wouldn't put random numbers so I'm just curious as to if there's a hidden meaning. Also, they don't look like some sort of company or government vehicles. They all vary in makes and models just as a regular resident's car.