Look at the star in Vizier to see the Spectral Energy Distribution (SED) of the continuum. The spectrum of all stars is approximately a black body (see https://lco.global/spacebook/light/black-body-radiation/). The shape of the spectrum is the same, it just shifts to longer wavelengths for cooler stars and bluer wavelengths for hotter stars. The accretion disks around young stars also approximately emit black body radiation. But the disks are much cooler. Thus, the combined spectrum of star and disk has two humps – and we call the hump from the disk infrared excess, as it is additional emission at infrared wavelengths compared to just seeing the central star.

This example curve shows an extra hump to the right / longer infrared wavelengths.

Turck-Chièze, Sylvaine & Couvidat, S. & eff-darwich, Antonio & Duez, Vincent & García, R. & Mathis, Stephane & Mathur, Savita & Piau, Laurent & Salabert, David. (2011). The long term dynamics of the solar radiative zone associated to new
results from SoHO and young solar analogs.