A tender is a request by, for example, a company or government department(s) seeking supplier(s) of goods or services. The tender documentation will set out the requirements, timeline, criteria, etc, and will often include a response template and a draft agreement/contract.
A bid is a potential supplier’s response to a tender. It must answer all questions asked in the tender documentation and must include all information requested, including proposed costings, if required.
This is a simplistic explanation, but it does clarify the difference between ‘tender’ and ‘bid’. Hope it helps.