The Gateron Yellow is a linear switch designed and manufactured by Gateron, to along with their line-up of linear switches such as the Gateron Red and Gateron Black. The Gateron Yellow is a linear switch with distinct similarities to the Gateron Red, with a slightly heavier spring at 50g actuation versus the Red's actuation at 45g. In this sense, the Gateron Yellow is essentially a slightly heavier Gateron Red, and in my experience, that holds true.
Looking at the stem, it's about as standard as a linear MX stem goes, with the iconic MX top piece, and the smooth legs on the front of the stem. In Gateron's case, the material of the stem is extremely smooth, similar to their Gateron Red and Gateron Ink Black stems in particular. The stem is in a bumblebee yellow, and is quite literally the same as the Gateron Red's stem, just with a different color.
The Gateron Yellow takes lubing well, I lubed Gateron Yellows with Tribosys 3204 and it improved smoothness a lot, as well as increased the 'thock' sound signature. This is again similar to the characteristics to the Gateron Red, and I can't convey just how similar this switch is to a Gateron Red.
In essence, the Gateron Yellow is a Gateron Red with a heavier spring, it shares the same housing characteristics as the Gateron Red, whilst also inheriting the lubing capabilities of other Gateron linear switches. I have previously reviewed the MX Red, and used a Gateron Red as the example there, you can read the review here.