The Maker token (MKR) is the MakerDAO native token. It acts as a utility token, governance token and a recapitalization tool for the MakerDAO platform, which manages the DAI stablecoin. MKR is used as part of the stabilizing mechanism that is in place to combat the price volatility of the DAI stablecoin.
DAI is pegged to the US dollar and has collateral in place to ensure stability. The MKR token is used is to pay for the "collateralized debt positions" (CDPs) that have been used to generate DAI. After this MKR is used, it is removed from the supply. MKR holders also contribute to the governance of the MakerDAO and vote on crucial issues related to the direction of the DAI stablecoin.

TrueUSD is a stablecoin backed by USD. It was created by TrustToken, a company that specializes in creating asset-backed tokens on the Ethereum blockchain. TrueUSD is fully collateralized and is transparently verified by third-party attestations.
TrueUSD was created within a legal framework that enables users to exchange USD directly with an escrow account. The platform is powered by smart contracts that ensure a 1:1 parity between USD and TrueUSD. Escrow accounts and regulatory compliance practices enable auditing and more legal protection for token holders.
Users wire funds to these third-party escrow accounts, and an equivalent amount of TUSD is generated to their ethereum addresses. Each TUSD can be redeemed for one US Dollar, that is held in escrow.

nUSD is a stablecoin that is pegged to the UD Dollar. It was created by Havven, a decentralized payment network. nUSD has a dual token mechanism that provides stability. In order to generate nUSD, users must acquire Havven Coin (HAV) and lock it in a smart contract. 80% of their HAV holdings remain in collateral, and 20% of its value is generated in the form of newly minted nUSD. This collateral staking mechanism includes an incentive mechanism that rewards users with a portion of the transaction fees that are collected when nUSD transactions occur on the network. nUSD is currently an Ethereum-based token, but will soon be transferred to EOS.