Can somebody please define me what a type, subtype, and supertype is in Magic: The Gathering?

Starting with 'Type' first, the card's Type is the card's basic classification - Land, Artifact, Enchantment, Sorcery, etc. Some cards can have multiple types - 'Artifact Creature' for example.

If a card has a word before any of its Types, this is a Supertype. Each Supertype has specific rules attached to it - Legendary, Basic, World, etc. These are not 'types' and are not affected by things that can change a card's Type.

If a card has words after its Types, these are subtypes. These don't have any specific rules attached to them, but they give the card a specific identity for the purposes of  spells/abilities that specifically look for or affect that subtype. Subtypes include things like Human, Elf, Goblin, Wizard, Cleric, Bird, Spider, Crab, for Creatures, Equipment for Artifacts, Aura for Enchantments, etc.