The ability to cast spells at a time when they are still relevant to the game is vital to an ever-hastening game. As more and more powerful effects get printed at lower and lower mana costs, decks can ill afford to suffer from not having lands (mana screw), having too many lands (mana flood), or not having the right colors (color screw). Different types of ramp do these jobs in different ways.
Permanent-based ramp provides incremental advantage turn after turn, but requires a sacrifice in order to do so. The first few turns are spent setting up for either big spells or chains of spells later, which puts immense pressure on the spells themselves. By contrast, Single-Use Ramp is either instant/sorcery-based or requires the sacrifice of a permanent for a quick burst of mana. These spells require less of a setup and frequently can catch a table by surprise.
Rituals
Rituals provide quick bursts of mana. They do so by either sacrificing permanents for mana or making mana through Instants and Sorceries. Either way, the mana usually has to be used the same turn it is made. Some provide small amounts of mana, like Lotus Petal and Pyretic Ritual, while others create big turns, like Mana Geyser and the infamous Dockside Extortionist.
Land Search-
These run the middle ground between Rituals and Mana Rocks, putting permanent mana sources onto the battlefield while providing a single-use effect. Rampant Growth and Explosive Vegetation effects add lands and can fix colors, while Sakura-Tribe Elder works with creature synergies, like a Mana Dork. They also provide deck thinning, which, while not statistically impactful, reduces the amount of lands remaining in the deck and increases the odds of drawing nonland cards.
Reanimation-
Reanimation refers to spells that put a permanent onto the battlefield from the graveyard. It can be considered ramp if the permanent being put out has a much larger mana cost than the spell being used to put it out. For example, spending 1 mana to Reanimate a 6-mana Grave Titan is like a 6-mana Dark Ritual. Granted, this takes some setup, which is where Rummaging and Looting come in.
Sneaking (legally)-
Sneaking refers to putting a big threat onto the battlefield or a big spell onto the stack from the hand without paying the full cost. Some permanents can do this repeatedly, like Quicksilver Amulet and the poster-child for the effect, Sneak Attack. Others do this once, like Dramatic Entrance or Through the Breach. These effects work particularly well with large creatures that have enters-the-battlefield abilities.Â