AirPort Express Base Station (Generation 1, 2004)

The AirPort Express Base Station was part of Apple’s AirPort line of wireless products. Although its design was more compact and it had fewer features than the AirPort Extreme Base Station available at the time, the AirPort Express Base Station included the ability to receive streamed audio from a wirelessly connected computer that was running iTunes. The AirPort Express Base Station could play the streamed audio through speakers connected to its analog/digital audio output jack, a feature the AirPort Extreme lacked.

The original AirPort Express offered 802.11g wireless, contained an analog–optical audio mini-jack output, a USB port for remote printing, and one Ethernet port. The AirPort Express could only stream audio to a powered speaker or stereo system via iTunes—it could not stream video.

Source: Wikipedia

AirPort Express 802.11n (Generation 2, 2012)

The AirPort Express Generation 2 functioned as a wireless access point, to extend the range of a network, as an Ethernet-to-wireless bridge, as a print server, and/or as an audio server. This model allowed up to 50 networked users using the 802.11a/n Wi-Fi standard.

Connectors included an audio connector that combined a 3.5 mm minijack socket and a mini-TOSLINK optical digital connection. On August 28, 2018, AirPlay 2 support was added to the Generation 2 AirPort Express, giving it features similar to HomePod.

Source: Wikipedia