Bourdais raced in Champ Car. The IRL – which is essentially the present IndyCar Series – was a breakaway from Champ Car (which was then called CART) that started in ’96. The two series ran in competition until 2008, when Champ Car fell apart and the IRL/IndyCar absorbed what was left of it.
The significance of it, to me, was that they’ve previously been a bit sniffy about acknowledging Bourdais’ Champ Car achievements, as if they didn’t exist because they happened in the rival series. So it was cool to hear him called a four-time champion, which he is. They don’t count as IndyCar titles, but they’re indycar (as in American open-wheel) titles. It’s all very messy, just good that there’s one series now.