One thing which is useful to understand about car seats in Europe is the Group system. And even that has become horribly complicated so I shall explain from the basics. I'm going with R44 standards here, because R129 is different, but R129 seats are currently being produced roughly in line with R44 groups anyway, so it's still the most useful to understand.
Group 0+
Probably what you're using right now. This covers weight category 0-13kg and usually fits birth to about 15 months. The most common type of seat in this category is the carry handle type seat which is sometimes compatible with a pushchair. These seats are always rear facing except for a couple of specialised lie-flat ones which go sideways. But this group can never be forward facing.
Group 1
This category covers the weights 9-18kg and is sold as being from 9 months to 4 years. These seats can be forward or rear facing and are most commonly sold as a (relatively) permanent fixture in the car with a harness. You can also get seats in this category which use an impact shield, these are forward facing seats.
Group 2 and 3
This is a slightly more confusing category but basically covers high backed boosters and backless boosters, both used with the adult seatbelt rather than an integrated restraint system. They're usable from 15kg (highback) or 25kg (backless) but highback boosters are always sold as Group 2/3 so cover the top end of the weight scale too (up to 36kg - but realistically - no top weight limit). With modern car seats the reason it's useful to have these separated out is that combination car seats sometimes cover group 2 but not group 3, meaning that the seat will have a maximum usage weight of 25kg - but more on combinations in a second.
Got that? 
Right. Then more recently manufacturers have started producing combination car seats. So you used to get the following "basic" combinations:
Group 0/1 or Group 0+/1
- These are seats which are rear facing for Group 0 (babies), but then install forward facing for toddlers. They're not designed to be taken in and out of the car. If you look at these be careful to check the maximum rear facing weight, because sometimes it's lower than the standard 13kg (for complicated historical/cost cutting reasons I won't bore you with). This used to be a good alternative if you wanted to rear face for longer than a Group 0+ seat alone, because the seat shell is taller, meaning you usually get the full 13kg out of it (for most children, around 2-2.5). These days it's much easier to find a seat which covers Group 1 rear facing meaning it will last much longer, so this kind of compromise isn't necessary.
Group 1/2/3
- These are seats which start off with a harness (or impact shield) for Group 1, but are designed that when your child gets to about 3 or 4 years old you remove the harness and it converts to a high backed booster you can in theory use until they no longer need a car seat.
THEN, "Extended Rear Facing" or ERF became more popular. For the purposes of this discussion, ERF is rear facing in any weight group past 0+. (Rough age: Rear facing past a year old.)
So you now get lots of combinations but the main ones are:
ERF Group 0/1 seats - Essentially, a rear facing Group 1 seat which can also be adapted for smaller babies and used from birth.
Group 0/1/2 seats - A seat which covers from birth to 25kg - This is usually although not always harnessed right the way through to 25kg, rather than converting to a seatbelt booster. Check the individual description. Usually ERF to Group 1, occasionally to Group 2.
ERF Group 1/2 seats - Usually, a seat which is RF harnessed for Group 1, and then either harnessed RF or harnessed FF for Group 2.
Group 0/1/2/3 seats - Often marketed as "The only seat you'll ever need". The Joie one is, I believe, okay. Steer massively clear of these seats as sold by the cheapest brands like Nania, babystart, own branded seats. It's unlikely you'll find this combination as an ERF seat. I don't think this option is useful for most people, I think it's a false economy in terms of safety. What they are useful for (especially the Joie) would be somebody like a childminder or grandparent needing a spare seat which will potentially be used by children of different ages, who doesn't want to have to store several extra seats. For somebody looking for a seat which will primarily be used by one child, I think it's better to get something with fewer groups involved.
Ummmm yes did I say it was complicated? 