The main deck has non-engine cards that are needed to cover the most meta matchups, while the side deck is used to add more coverage for these matches and to have responses to more random rogue decks that players would be likely to see in the early rounds of regional events
Extra Deck 15 Gullveig of the Nordic Ascendant X LIGHT Link 1 [ Fairy / LinkEffect ] ATK 800 DEF - 1 Level 5 or lower "Nordic" monster If this card is Link Summoned: You can banish up to 3 cards from your hand and/or field, and if you do, Special Summon that many "Nordic" monsters from your Deck in Defense Position, also, for the rest of this turn, you cannot Special Summon monsters, except "Aesir" monsters, nor Normal Summon/Set any monsters
For example, to Synchro summon, you need to tribute a Tuner monster and another monster with a specified combined level - make sure that your deck can fulfill both requirements
By the end, youre given the aptly named Starter Deck to use in a game against the CPU