What is this and how do you play this?
There are similar questions around, and this is sort of answered already. The left hand contains two separate 'voices'. The higher one keeps moving upwards, while the lower one stays on and holds the low A. It just happens that both 'voices' start on that same A.
On a keyboard instrument, it means the same as the first example below.
If the long note was a half-note rather than a whole-note, it is often written as in the second example.
In an orchestral score where the parts for two instruments are written on one staff to save space, it means that one instrument plays the four 8th-notes, and the other instrument plays the whole note.
I would read this as (assuming bass clef) holding the A for 4 beats and the rest of the notes in the arpeggio are not held until you get to the C. this is all done in the left hand.
It shows a musical intention, not precise instructions for playing technique. The low A is to be sustained throughout the bar, it is also the first note of the LH arpeggio. Think of the piano emulating two instruments if you like - a cello and a harp! Unless the player has very large hands, use of the sustain pedal is implied.
This implies playing two voices with the left hand, both starting on low A, but one continues and the other stays. So basically you hold the A for the whole bar, but its character and relation to the next eighth note must be such that the listener also perceives it as the starting note of a phrase in eighths.
This implies that the eighth phrase cannot be phrased as staccato (as you could not play its first note staccato), it implies that the phrasing of the remaining three eighths in the first two beats does not suggest an anacrusis or upbeat (in which case it could start minisculely late with a tiny acceleration and its weight focused on the following beat rather than the previous one).
In short, even if your execution cannot actually play two notes at once on a single-manual keyboard, the rendition should be as consistent with the indicated presence of two voices with a common starting pitch as possible.
If you are a Midi robot, forget about all that phrasing mumbojumbo and just put the key release event for the starting note at the end of the bar.