Firelink Shrine is Dark Souls: Remastered’s hub. On your first visit here, you’ll meet a few useful NPCs — the Crestfallen Warrior who serves as a guide to what you’re doing in the game, the mute Ash Maiden who will upgrade your Estus Flask, and Petrus of Thorolund who can sell you miracles. (If you wander down a little way into the New Londo Ruins, you’ll be able to meet the blacksmith Rickert of Vinheim much earlier than you’ll encounter Andre of Astora.) As you progress through the game, more NPCs and vendors will appear here.
Firelink serves as your hub for the rest of Lordran. There are paths to and from Undead Burg, Undead Parish, Lower Undead Burg, The Catacombs, and New Londo Ruins. When you finally free the elevator from Undead Parish to Firelink, you’ll be able to interact with Snuggly the Crow both to trade shiny items and to return to the Undead Asylum.
There are lots of items scattered around Firelink, which will help you earn some levels early. You can also find a few multiplayer-themed consumables and a weapons.
There’s only one bonfire in the area and no boss to fight. There are only a few enemies — low-level hollows on the path toward Undead Burg and very hard to kill skeletons in the cemetery on the way to the Catacombs.