Modeling amplifiers look like conventional guitar amplifiers but are primarily designed to emulate the sound of well-known modern and vintage amplification gear. They come in diverse speaker configurations and are able to provide a variety of sound at any volume. It’s also common to find guitar effects such as delay and chorus built into them. Because of this, it could be said that modeling amplifiers are both guitar amplifiers and effect processors.    

The appearance of microprocessor technology allowed the implementation of digital onboard effects in guitar amplifiers. This led to the creation of a huge variety of devices which we know as modeling amps. They’re capable of simulating the characteristic sound of different tube amplifiers, speaker cabinets, and even microphone placements and types. In many cases, these settings can be programmable from a computer or laptop via a USB connection.

Benefits of modeling amplifiers

Among other features, modeling guitar amplifiers give the player the ability to skip the on-stage speaker altogether. Instead, they can connect the output jack of the amplifier to the main sound system. This gives the sound engineer absolute control over the volume level of the guitar on stage and on the main speakers. That kind of setup can be particularly beneficial in a worship environment, where noisy or loud guitar amps should be avoided.

This also resulted in increased use of “full range, flat response” (FRFR) amplification systems by guitarists. Before, guitarists did not commonly plug-in directly into the PA system or powered speakers. The reason for this is most genres and formats for live performance rely on the tonal coloration of a regular guitar amplifier setup. This coloration comes from the preamplifier, equalization filters, power amp, speakers, and cabinet design. We can get all that with a modeling amp, while we actually connect directly to the FRFR system.

Modeling amps are built on computers and chips, so they’re quite light and portable. This can be especially useful if you need to cycle through several tones over the course of a set, but don’t fancy carrying several amps or pedalboards to the venue.  

Also, we can see other advantages when we compare them to tube amplifiers and their glass tubes. These have fragile delicate filaments, they can be noisy make noise and we need to replace eventually. 

https://en.wikipedia.org/wiki/Guitar_amplifier#Modeling

https://www.fender.com/articles/gear/the-many-benefits-of-modeling-amps