Ground-type Pokémon are not damaged by sandstorms, and are immune to Electric attacks. Despite their immunity, they can still become paralyzed.
Ground is the only type super effective against Electric, and is super effective against five types in total, tying with Fighting for the most super effective matchups.
Because Ground is so useful offensively and resisted by so few types, Ground often provides good coverage when combined with another type of attack. It does particularly well when combined with Ice, as Ice's strong matchups include Grass and Flying.
Ground attacks cannot hit Pokémon under the effect of Magnet Rise or Telekinesis, though all Pokémon lose their immunity to Ground when they are grounded (such as by Ingrain, Gravity, or Thousand Arrows). Further, most Ground-type Pokémon can learn Rock-type moves (mainly those available via TM such as Rock Slide) to check Flying-types, along with Bug-types and Ice-types.
Disclamer: Rarity of an individual Pokemon can and does vary depending on the spawn location. In the table below the lowest rarity is presented. Please check individual routes for more information on the rarity of your desired Pokemon.
Disclamer 2: All Pokemon names and locations contain a hyperlink to their pages. Links have been colored black for design purposes. Please note that not all pages are of quality or even exist, work in progress.