B+W Filter 49ES 489 What would it be used for?

I picked up a B+W 489 filter at a car-boot sale years ago. I had no idea what it was but it was only a few pennies.
I was rooting through my box of misc camera bits yesterday and found it again. I did a bit of googling and worked out that it's some sort of IR cut filter uut I'm not sure what it would be used for in practice. could someone fill me in?

So its more for older digital/cctv cameras.

Ta

The 486 and 489 can be used with D-cameras that have been converted to IR sensitive (so called hot mirror/filter removed), when you want to block IR light (to use them again in 'regular' mode.)