If you are looking for a Boston condo for sale you may want one that has more than one bathroom. You may find a listing for a downtown Boston condo that has two bathrooms only to find that one of the bathrooms is a 1/4 bath which consists of just a toilet.
A full bath, which counts as one bathroom has a shower, tub, toilet, and sink.
A three-quarter bath has a toilet, and a sink, and a shower
Most half baths sometimes called a “powder room” have a toilet and a sink
Quater baths which also count as one bathroom may have a toilet, or a sink, or a shower, or a tub.
The most unusual combination of baths I have ever seen in a house was one where there were a tub and a sink on the second floor and a toilet and a sink on the first. That house had 2 half baths and was listed as having two bathrooms.
Bathroom definitions are likely local so don’t take this too seriously if you are house-hunting outside of downtown Boston