what is the equivalent to a bachelor degree?

When an employer uses the term equivalent, it typically means they will consider any job-related experience that will provide the candidate the necessary knowledge, skill, and abilities (abbreviated "KSA") to be able to perform the functions of the advertised position proficiently. A formal education with a four-year degree can be sufficient to provide a candidate with necessary KSAs. Or, a high school diploma and four years of experience in a particular job can also help a candidate develop sufficient KSAs. A company is simply looking for someone who has the KSAs, whether from an informal background or through a formal avenue, to perform the functions of a job successfully.

Generally it refers to whatever first post-secondary degree or diploma might be awarded in a foreign country. In another country, it might not be called a bachelor's, and the process for earning it might be different, too, especially in certain subjects and fields.

No, "experience" is usually helpful, but it's not considered the "equivalent". The employer is referring to education/training.