No, a base layer is not the same as thermals. While both provide insulation and keep the wearer warm, there are key differences between the two. A base layer is a lightweight, form-fitting garment worn close to the skin.
On the other hand, thermals are a type of base layer specifically designed for colder temperatures. They are usually thicker and provide additional insulation. Thermals are often made from fleece or synthetic fibers, which trap body heat and keep the wearer warm.