Slovakia is a signatory to the Schengen Treaty.
Border restrictions are usually not required between nations that have signed and implemented the pact. This covers the majority of the European Union as well as a few additional nations.
Before boarding foreign planes or boats, passengers’ identities are typically checked. Temporary border restrictions are sometimes used at land boundaries.
A visa issued to any Schengen member is also valid in all other countries that have signed and implemented the treaty.
Recognized refugees with a valid travel document issued by the government of any of the following countries/territories are free from getting a visa for Slovakia (but not for any other Schengen nation save Germany and Hungary) for a maximum stay of 90 days in a 180-day period.
Slovakia just recently joined the Schengen region, therefore local cross-border transit services may be restricted in certain locations, but this is changing and crossing is quite simple in some places. You should carry ID with you normally, but to minimize trouble, maintain an ID with you in border areas.
If you need a visa, always apply at an embassy ahead of time. You have no possibility of getting a visa at a Slovak border, regardless of how you arrive or your nationality.