Hello Sarah, baseband refers to the original data signal (without up-converting with high frequency carrier), whereas passband refers to filtered signal that was originally modulated onto a carrier. I think it would help if you think of the differences in terms of spectral occupancy and whether it is filtered or not.

Baseband transmission is transmission of the encoded signal using its own baseband frequencies; i.e. without any shift (up-converting) to higher frequency ranges, while passband transmission is the transmission after shifting the baseband frequencies to some higher frequency range (called passband) using modulation (which can include passband filtering to ensure that our signal is separate in its passband from neighbouring passbands). Base band frequencies range from near zero to 4KHz for telephony voice while the camera video output up to 5.5MHz. 

Communication using baseband is limited mainly to wired communication. For example in a CCTV (camera and monitor), the video is sent directly over a coax cable. Note that baseband communication can be either analog or digital. Communicating using baseband over air is limited as the low frequencies will be mixed with other baseband frequencies .

We to resort to passband communication to send over air as well as over wires in order to multiplex many signals together. Hence, sending phone calls over a cable connecting exchanges in different cities or over a satellite link requires that the baseband (0-4KHz) signal be shifted to somewhere in the MHz or GHz to set together alongside other shifted baseband signals (other calls). You need to demultiplex and shift down (demodulation) to baseband frequencies at the other end. Thanks. @AlDmour.

The above written statements are well defining the terms asked. I want to add its some more things related to digital communication system.

In baseband transmission, line coding is utilized, resulting in a pulse train or pulse amplitude modulated (PAM) signal. This is typically used over non-filtered wires such as fiber optical cables and short-range copper links, for example: V.29 (EIA/TIA-232), V.35, IEEE 802.3, SONET/SDH.

In passband transmission, digital modulation methods are employed so that only a limited frequency range is used in some bandpass filtered channel. Passband transmission is typically utilized in wireless communication and in bandpass filtered channels such as POTS lines. It also allows for frequency-division multiplexing. The digital bit stream is converted first into an equivalent baseband signal, and then to a RF signal. On the receiver side a demodulator is used to detect the signal and reverse the modulation process. A combined equipment for modulation and demodulation is called a modem.

In a baseband transmission, the entire bandwidth of the cable is consumed by a

single signal.

In broadband transmission, signals are sent on multiple frequencies,

allowing multiple signals to be sent simultaneously.

The above answers are satisfactory. The information signals as the voice, the audio and video as well as data inform ob binary digital signals are all base band signals occupying the power range of the frequency spectrum. They can be transmitted in the form they are generated. This called base band transmission such as fixed telephone line. In order to transmit the signal at higher frequency bands one has to shift the baseband frequency to the required frequency band by a process called mixing or modulation. After frequencies shifting the resulting frequencies will cover a band of frequencies centered around the carrier frequency which has then a pass band characteristics. Therefore this signal is called pass band signal. In fact all the wireless communication systems are band pass system.

Best wishes

In addition to the above answers, we can say:

Baseband transmission is done for the signal without modulation, and it suits short distance communication.

Bandpass transmission is done for the modulated signal shifted from baseband frequency to a higher frequecy, and it required in a long distance commmunication.

Thanks and regards

Passband transmission you can do modulation and multiplexing. Because the frequency is high you can use a small antenna.

Baseband channel is from 0 to W Hz. To use this channel fully we use a time domain signal that has an FFT that in constant from 0 to W Hz.

https://www.polytechnichub.com/difference-baseband-transmission-bandpass-transmission/