The short answer
A PCB is the bare printed circuit board. A PCBA is a board with components assembled onto it. When requesting a quote, state whether you need bare boards, assembly of supplied boards, or PCB fabrication and assembly together.
Start with the deliverable
A bare-board request describes the circuit board construction: layers, material, thickness, copper, finish, drilled features and outline. An assembly request also describes the components and how they are populated. Naming the finished deliverable helps avoid comparing a bare-board price with a price that includes parts and assembly.
Prepare the right files
For fabrication, prepare Gerber or other agreed fabrication data, drill files, a drawing and stackup requirements. For assembly, add the BOM, placement data and assembly instructions for the same revision. Identify parts that must not be fitted and any options that differ between variants.
Decide who supplies the components
Explain whether components will be supplied by you, sourced for the project or divided between both parties. Identify approved alternatives and parts that cannot be substituted. Sourcing decisions should remain connected to the approved BOM rather than being inferred from a generic service name.
Separate board testing from assembly testing
Bare-board electrical testing checks circuit connectivity within its agreed scope. Assembly inspection and functional testing address different questions. Specify inspection requirements and, where needed, the operating conditions and expected results for a functional test; do not assume that one test covers the other.
Make the quotation comparable
Include board revision, service scope, quantity, destination and required ship or arrival date. Ask suppliers to distinguish fabrication, components, assembly and agreed testing. Compare the same deliverables and exclusions before selecting a manufacturing route.