Soft resetting (often shortened as SRing) is a feature found in the main series Pokémon games, with the exception of Pokémon Colosseum. It involves pressing certain buttons on the game system to reload the game from the startup screen. The term "soft reset" is to differentiate from a "hard reset", which is restarting the game by powering down the console and then turning it back on again.
This practice is widely considered useful, as rebooting the game will modify hidden data values. The values that determine the shininess of an in-game event Pokémon is of particular interest here, as are the Pokémon's IVs and Natures. Soft resetting eliminates the need to constantly turn off (and on) the game when attempting to get a Pokémon with these specific qualities. Although time-consuming, it is a widely practiced method to get a desired Pokémon.
When soft resetting for a Shiny Pokémon, another similar term, Shiny resetting, can also be used.
DS games: Press and hold L, R, Start, and Select.
I have not heard about hard reset so sorry
Hope I helped