For the purpose of your visit, each country provides various types of visas. Even though you can apply online for a visa in most countries. It will take you some time to understand the procedure, get the documentation needed, and fill out the application form. You must ensure that you fulfil the criteria and requirements for eligibility relevant to the country to which you choose to travel.
Note that there are various conditions for a student visa, a visitor visa, a work visa, etc. You must know the basic conditions of the visa that you are applying for and fill out the application form and follow the other procedures for obtaining your visa.
The general guidelines for a Visa application are below: