In North American theological language, “charismatic” and “Pentacostal” aren’t totally identical: “Pentacostal” is a particular kind of “charismatic”.
“Charismatic” groups emphasize the gifts of the Holy Spirit, and can be denominations or can be organizations within a larger communion – there are several charismatic Roman Catholic groups for example, and a Southern Baptist congregation might or might not be charismatic. By the last estimate I’ve seen, up to 1/4 of Christians in the world are charismatic. It isn’t surprising to find some universalists in there, too. Some of the famous Tennessee snake handler Baptists are universalistic, but all snake handling churches are charismatic churches (though not all charismatic churches go for snake handling, to say the least! Nor all Baptists, or my Mom would be Catholic I expect.
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“Pentacostal” groups have strong agreements with each other on more particular ways and doctrines concerning charismatic activity, the Assembly of God being one such group (and maybe the largest). Last I heard there are a little more than 4% of Pentacostal Christians.
A quick example of distinction is: a charismatic church or group might or might not think speaking in tongues is a gift given to all Christians as a sign that someone truly has been baptized by the Holy Spirit and so is truly a Christian; but a Pentacostal (so far as I know) definitely believes this (although they might disagree among each other about how it applies or works). That’s why they have the description “pentacostal” because they’re referring to the first Christian Pentacost when the Spirit descended on all the Christians gathered with the apostles and they all started speaking tongues for evangelizing the people in Jerusalem.
And now you know more than you ever wanted to know about charismatic and pentacostal groups. 