It’s E7 with fifth flattened, which is notated as E7(-5). The chord website probably simplified the chords for ease of playing, which is kinda common practice.
By flatting fifth, the note B becomes B♭—In solfa, Re becomes Re♭. Theoretically it strengthens the pull toward the tonal center. And, of course, being a note outside the key, this also provide an intriguing ear-catching stimulus.
Such chords are called “altered dominants”, explained in the chapter V of Chord edition, though not translated yet.
