[Closed] l/s breathable shirt and l/s base layer... whats the difference ??

fit, baselayers should be like a second skin, not loose and flappy.

Breathable here means taking sweat (in the form of vapour) and keeping away from your skin to make you feel less clammy. You can get man made fibres to this, but they can start to wiff unless you wash them regularly, or alternatively you can get a fine wool called merino, which has many desirable properties, such as lack of smell temperature balance, and so on, but at a price (normally about 3-4 times as much).

it depends

I have a berghaus top which calls itself a base layer. Its a similar fit to a loosish jersey - and only really works as eigher a jersey in its own right, or an extra layer if its cold. Apart from the lack of pockets there is no real advantage to wearing it under a jersey than just wearing 2.

I have recently bought a tight fitting "hot" base layer for summer use. This seems to work well at keeping me dry, wicking sweat away from the skin

I don't seem to get so cold when the temprature drops as I don't have lots of sweat on my skin ready to get cold