What is the difference between weather radar data and weather forecast?

Weather radars provide past and current info about the movement of precipitation. This is the actual info based on the sky screening as is. Radars typically detect moderate to heavy precipitation with extreme accuracy, though they may sometimes have nuances with the detection of light rain or drizzle. Radar data also allows you to build a short-term (up to 90 mins) accurate precipitation trajectory. A weather forecast is an algorithm that makes predictions for further long-term precipitation movement. Forecasts are based on mathematical formulas and may not always be accurate for the next hour.

What’s the difference between the radar and satellite map layers?

The radar layer can show more details than the satellite layer. Radars can even detect small storm cells, while satellites see precipitation globally all over the Earth. Additionally, radar animation is of higher quality than satellite animation.

What is Color Bar Image?

The side color bar on a radar image displaying dBZ represents the reflectivity of the radar signal. dBZ stands for Decibels of Z, where Z is the reflectivity factor (a measure of the density of objects reflecting the radar waves), and dB is decibels, a unit used to measure signal intensity.

The dBZ values shown on this color bar in radar images are numerical indicators of the intensity level of signals reflected back from rain or other detectable phenomena. A higher dBZ value indicates a higher density of rain or potentially smaller, more numerous raindrops.

Here's a general reference table:
Less than 20 dBZ: Light rain or no rain
20-30 dBZ: Light to moderate rain
30-40 dBZ: Moderate to heavy rain
40-50 dBZ: Heavy rain
50-60 dBZ: Very heavy rain
Above 60 dBZ: Extremely heavy rain
Using dBZ values is a common practice to estimate the density of rainfall in radar imagery.

What is UTC or GMT Time?

Weather observations around the world (including surface, radar, and other observations) are always taken with respect to a standard time. By convention, the world's weather communities use a twenty four hour clock, similar to "military" time based on the 0° longitude meridian, also known as the Greenwich meridian.

Prior to 1972, this time was called Greenwich Mean Time (GMT) but is now referred to as Coordinated Universal Time or Universal Time Coordinated (UTC). It is a coordinated time scale, maintained by the Bureau International des Poids et Mesures (BIPM). It is also known as "Z time" or "Zulu Time".

You can check the worldwide time at https://www.timeanddate.com/worldclock