Viewmodel
Viewmodels are a visual representation of the player's active weapon, shown on the player's display. Viewmodels show the player their active weapon and display various unique animations for firing, reloading, or inspecting their weapon. Overall, along with the heads-up display, viewmodels are an integral part of the game's UI for quickly relaying information to the player about their active weapon.
While viewmodels are a very important part of Team Fortress 2 gameplay, for some players they may pose a problem in that their viewmodel is too large and takes up too much of their screen. Several remedies currently exist for this problem; a player may increase their viewmodel field of view via the console command viewmodel_fov to position the viewmodel further away/closer to the display, enabling minimised viewmodels, or simply turning off their viewmodels altogether (a particularly popular option in competitive matchmaking). A player's viewmodel configuration ultimately comes down to their personal preference.
Minimised viewmodels
Minimised viewmodels (also referred to as viewmodel minmode) are a feature introduced in the Meet your Match Update, created to remedy the problem of viewmodels taking up large portions of the screen, even at higher viewmodel FOVs. When enabled in the Advanced Options menu or by using the console command tf_use_min_viewmodels 1, it makes the player’s viewmodel smaller and lowers it, positioning it closer to the bottom center of the player's screen, allowing the player to see more of the battlefield (e.g. objects that may have been covered by the player’s viewmodel, such as Stickybombs, or flanking enemies like Spies and Scouts) while still being able to see their active weapon. Overall, minimised viewmodels have widely replaced entirely disabling viewmodels and transparent viewmodels as it still enables players to see their weapons while increasing visibility.
