[bhdzllr]

Not necessarily, but it might be faster.

Basically you need map data (in form of tiles) and you need a way to show and interact with your map (e. g. Leaflet).

Here is a summary and one way to do it: https://switch2osm.org/the-basics/

Tiles can be images or vector based. I also recommend having a look at https://openmaptiles.org/ if you want vector based tiles. You can generate your own tileset with this (output is a mbtiles SQLite file based on a open source schema; the schema describes which information go into the database and later can be shown) or download a set of tiles (because e. g. for the world it will take a lot of ressources and a long timeto generate a tileset). There are also servers (like tileservergl or tileservergl-light) that can serve the tilset - not only as vector tiles but also as graphical image tiles.

Raw OSM data can be downloaded for free from https://download.geofabrik.de/