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STB = "Set Top Box" - nowadays this is usually a single tuner conversion unit though PVRs are also set top boxes.
PVR = "Personal Video Recorder" usually having a "Freeview +" sticker in the UK if you want to use your existing aerial.
PVRs usually have two tuners. Both record to a hard disc of the sort you have in computers. One is used to record another programme while you watch the other one "live". The "live" programme can be paused if, say, you have a telephone call in the middle of a show. When your call is over, you can resume watching from where you were interupted. You can then "fast forward" through the ads to catch up with the live broadcast.
PVRs are also marketed by Sky as "Sky+" boxes, Freesat as "Freesat +" boxes (for these two you need a satellite dish) and Virgin Media do a "V+" box for their cable service. Freeview + and Freesat + boxes are sold as retail items. Sky+ and Virgin V+ come as part of a subscription. BT also do their "BT Vision" service which is a hybrid of a Freeview PVR and a box to download programmes via broadband overnight.
As I presume you have a computer, you could also get a "DVB-T stick" to go into the USB socket. This will convert your computer to receive Freeview broadcasts and it will also act as a simple PVR with the right software (Windows Media Center for example) Unless you get two "sticks", you will not be able to watch one programme while recording another but you can use your computer to record programmes while you are away.
These sticks usually come with a mini aerial that you may have to replace with an input from your standard roof aerial if the signal strength in your area is currently low.
(In advance of your next question, the European standard is now "DVB" for "Digital Video Broadcasting" - even though we in the UK also use it to relay radio stations in the spare "space" that digital gives. DVB has different "flavours" for different delivery platforms so S = satellite, C = cable and T = terrestrial or land based transmitter sites. DVB is now about 20 years old and they have a second generation which uses "2" after the flavour letter. Satellite systems use both generations but the terrestrial version is currently being rolled out for use as a high definition service. The UK is the first country to use it and you will see "Freeview HD" or DVB-T2 boxes from about £89, they also get standard DVB-T. I believe none have an "RF" output so would not work with the TV you currently are talking about. You also would not get High Definition pictures - until you replace it with a "flat panel" set. )
To answer your original question, as has been pointed out - you can use a SCART only box if you have another "RF" or radio frequency box to convert the SCART to a TV signal. Alternatively, an old VHS recorder can be usually pressed into service by using the SCART input and the RF or "aerial" output. This is a bit wasteful of power of course and there are both STBs and PVRs with such facilities built in.