A study visa is a government-issued immigration document granted by a consulate general or embassy, which allows you to legally study in a specific country for a specific date range. Your student visa is as important as your passport; without it, you will not be able to study abroad, if required by your host country.
Every country has its own process, requirements, and fees for applying for a visa. Some countries may require you to travel to an in-person appointment at a consulate or embassy in selected cities whereas some may require you to simply submit your documents at the registered embassy office.
Being granted a visa is a privilege, not a right. A consular office may deny your visa application, so it is best to adhere to their requirements and apply as early as possible.