Optifine is third-party software that represents a more advanced level of settings for the vanilla version of Minecraft.
In simple words, it is a Minecraft MOD that makes improvements in the frame rate of the game and enhances the performance by fixing some performance-related settings.
This one is the most downloadable modification of Minecraft. Not only it helps you to run the Minecraft with any lag but it is also helpful to increase the graphics of Minecraft so that you will get beautiful looks.
You can download all versions of OptiFine from the download section. To download OptiFine, head over to OptiFine and tap on download version as you want. Then, after downloading, run the file.
You can make adjustments in the settings if you want to.