Cross and delight of every player on PC, anti-aliasing is a filter that is applied on curved or diagonal objects to make them “smoother” and to show less the inevitable jerks (remember that the pixels are square and not spherical) . A little aliasing is inevitable, but this filter helps to reduce it and there are several AA technologies more or less effective and heavy in terms of impact on the framerate.
Supersampling Anti-Aliasing (SSAA): it is perhaps the heaviest AA method ever, but if set at high levels (for example SSAA 4x) it virtually eliminates all the MSAA (Multisampling Anti-Aliasing) scoring: it is not as effective as the SAAA , but if set at high levels it can prove really heavy for your GPU. However, MSAA is not applied to all objects and certain games in DirectX 9 (such as Mass Effect and other titles made with Unreal Engine 3) do not support this technology.
Alpha to Coverage (ATOC): this is an option that is found next to the MSAA in some games and is used to apply the AA filter on those objects (mostly transparent) not covered by the MSAA.
FXAA (Fast Approximate Anti-Aliasing) and MLAA (Morphological Anti-Aliasing): they are both rather light AA post-processing technologies introduced by Nvidia and AMD respectively. They are used if you do not have a particularly performing GPU because of their modest impact on the game’s framerate, but the result in terms of quality is far from what is offered by MSAA or SSAA.
SMAA (Subpixel Morphological Anti-Aliasing): a fairly recent filter that offers better antialiasing than FXAA and comparable to that of a 2x or 4x MSAA. Usually impacts on the framerate with a percentage ranging from 5% to 10%.
TXAA (Temporal Approximate Anti-Aliasing): exclusive AA filter for Nvidia cards which essentially combines MSAA and anti-aliasing in post-processing. It requires more GPU workload than MSAA and tends to blur textures slightly.
If your PC allows you, opt for a combination of 4x MSAA and FXAA or SMAA. Instead, avoid SSAA and TXAA, as the marginal improvements in image quality do not fully justify the drop in framerates.