There are two main types of visas available for travelers visiting Nepal: tourist visas and trekking visas. Tourist visas are intended for travelers who want to visit the country for leisure purposes, while trekking visas are specifically for those who want to go trekking in Nepal. Trekking visas typically require additional permits and fees.

Visas for Nepal can be obtained in advance from a Nepalese embassy or consulate, or upon arrival at Tribhuvan International Airport in Kathmandu. When applying for a visa in advance, you'll need to provide your passport, a completed visa application form, and one passport-sized photo. When applying upon arrival, you'll need to have a passport with at least six months of validity and the necessary fee in US dollars or local currency.

In addition to a valid passport, you'll need to have proof of onward travel and enough funds to support yourself during your stay in Nepal. You may also need to show proof of yellow fever vaccination if you are arriving from a country with a high risk of yellow fever transmission.

Tourist visas in Nepal are available for a variety of lengths of stay, ranging from 15 days to 150 days. The length of stay you select will determine the cost of your visa. Visitors can also apply for multiple entry visas if they plan to leave and re-enter the country during their trip.

Yes, it is possible to extend your visa while in Nepal. You can do this by visiting the Department of Immigration in Kathmandu. You will need to provide your passport and a reason for the extension. The cost and length of the extension will depend on your visa type and the reason for the extension.