What does the M105 / M155 line format (T:20.38 /185.00 @:127) mean?

The M105 G-Code for printer firmwares like Marlin prints lines such as

T:20.38 /185.00 @:127

The RepRap wiki has extensive documentation about those lines. Here are the most important ones

• T:actual /setpoint Temperature of the hotend in °C
• T0:actual /setpoint Temperature of the first hotend in °C (only if you have multiple hotends)
• T1:actual /setpoint Temperature of the second hotend in °C (only if you have multiple hotends)
• B:actual /setpoint Temperature of the heated bed in °C
• C:actual /setpoint Temperature of the printer case in °C
• @:value : Current PWM output value of the hotend. Typically, 8-bit PWM is used, so 255 is full-scale.
• B@:value : Current PWM output value of the bed. Typically, 8-bit PWM is used, so 255 is full-scale.