What is the difference between Tc, Ta in datasheets?

Question

Electronics

There are several power values ​​in the datasheets, but on the contrary the following values:
Tc = 25 °C
Tc = 70 °C
Ta = 25 °C
Ta = 70 °C
Ta is signed Surface Mounted on 1" x 1" FR4 board.
And Tc is sometimes signed with Package Limited.

What do these signatures mean? And what number to look at as a characteristic of the element?

Answer 1

Probably, Tc is understood as the temperature of the crystal. And under Ta - the environment (taking into account the recommended installation conditions - on a standard fiberglass with a copper thickness of 35 microns and its area of ​​1 sq. inch).
Specifics, would.