There are four types of VISA depending on the purpose and identity of the applicant:
The duration of stay includes 14, 30, 60, 90 days and starts from the next day of arrival. For extension, foreign visitors must apply from the Bureau of Consular Affairs or branch offices of MOFA before the due date with relevant documents.
For more info, go to: Bureau of Consular Affairs, Ministry of Foreign Affairs
For relevant info, consult Visa-Exempt Entry Regulations.