Visas are permissions granted to enter a country. They are normally stamped or glued into your passport by a consul, vice consul, or consular agent in the embassy or consulate of the issuing country. They usually tell how long they are valid for, how many entries they allow (single or multiple), and what your “status” is, such as diplomat, tourist, or on business.
Visas are not an indication of how much the host country wants you to visit. They are governed by the diplomatic game of reciprocity. This is where one country gets even with another. If the U.S. makes it hard for citizens of Slobovia to get in, then Slobovia is likely to put the squeeze on Americans asking for a visa, no matter how badly they want tourists and the money they bring. If they can’t simply refuse as many visas as America does (because they really want you to come), they’ll get even in other ways like delaying applications, charging fees, or otherwise making applicants jump backwards through flaming hoops.
Getting a visa is usually as easy, or as hard, as getting an application, filling it out legibly, attaching as many photos (of the exactly correct dimensions) as are required, and mailing it to the nearest consulate. [Note: Embassies usually contain consulates. The difference is that embassies are offices of Ambassadors who represent their countries in the host nation. Consulates, even in embassies, exist primarily to serve the needs of their own citizens and of persons wanting to visit their country.] After you mail the application, you wait. It’s a good idea to call the embassy in advance and ask them how long it usually takes, remembering that the information you receive may be inaccurate.
Keep in mind that the consular staff of a small country may be only one or two people, and they take off all local and national holidays of your country and theirs, besides taking annual leave and sick leave, and maybe only working 4-6 hour days. So, even if there aren’t many people applying for visas to Bhutan (for example), it may take a while.
What did I leave out?