Stellar makes it easy to issue assets and to connect them to existing banking rails so that users can move value onto — and off of — the network. The services that create those connections are called anchors, and you can read all about how they work and what they do in Enable Deposit and Withdrawal.
Most Anchors set up infrastructure to enable wallets to offer in-app deposits and withdrawals by following best practices specified in Stellar Ecosystem Proposals. SEPs are publicly created, open-source documents that live in a Github repository. They define how different institutions (such as asset issuers, wallets, exchanges, and service providers) should interact and interoperate. If you're building an app, you can implement the client side of some key SEPs and immediately give your users access to a whole world of local fiat currencies
This part of the tutorial will focus on the Interactive Anchor/Wallet Asset Transfer Server SEP (aka SEP-24), which defines the specs for deposit and withdrawal implementations. It's focused on the client side of interactive user flows — meaning flows where users interact with an Anchor-hosted interface rendered inside a wallet — and by the end, you should have an implementation which can be re-purposed to work with any SEP-supporting Anchor.
When you implement SEP-0024, users can tokenize their grocery-buying dollars, pesos, or naira, use them on the Stellar network and, when they're ready, redeem them for cash in hand or money in the bank — and they can do it all from the comfort of your app.
Most Anchors offer fiat-backed assets, and SEP-24 is set up to allow them to handle various KYC and AML requirements. But SEP-24 allows for the deposit and withdraw of cryptocurrencies like BTC, ETH, and ERC20 tokens like USDT. If the financial landscape is a bunch of lakes, SEP-0024 is a series of rivers by which you move your currency canoe in and out of the Stellar lake.