The plus signs and slashes are different factions claimed land, there will be more symbols if there are more factions with claimed areas on the radius of your map. You'll be able to see what symbol represents each faction at the bottom of our f map.
/f map on toggles on the f map as you go around so you dont need to keep typing /f map. If you want to toggle it off simply do /f map off Also the more factions claimed area that shows on the f map, the more variety of symbols Hope you understood
The blue plus sign is you and all the slashes and other symbols are factions. Under the f map you can see which faction it is.