So far, I thought these meant the same, but job postings on job sites mention them separately.
What is difference between "Offers Relocation" and "Offers Visa Sponsorship"?
They will pay some or all of your moving expenses. They can offer a fixed amount, they can offer actual expense, or they can offer actual expenses up to a limit. In some cases they can actually help make arrangements including offering a period of time in corporate housing. Some will even pay for a trip to the new city to house hunt.
Depending on the extra benefits they offer, there can be tax implications. Also the more they pay the more likely there will be requirement for you to stay with the company for a minimum amount of time, or you will have to pay them back.
Watch the tax rules regarding minimum distance of the move and the number of months you have to stay and work in the new location, or what you though was free help could be taxable.
Offer Visa Sponsorship
They will help you get a Visa to work in this country. They may also help a family with the paperwork to move to this country. They may be tolerant of the starting date because they know that a Visa takes time. There will be requirements regarding how long you are expected to work for them, in addition to any legal requirements regarding work rules.
The company can offer you one, both, or neither of these options:
Relocation: They offer to help pay for a move with all the usual limits and tax rules.
Visa Sponsorship: They offer to help with all the visa paperwork, possibly including all associated fees.
What they offer, and why they offer it, is because they have found they need to offer this type of help in order to attract the number and quality of employee they are looking for. If they can find enough candidates that don't need help, they will not offer help.