Pacaya is an active volcano that showed spectacular eruptions for several years. There is still some volcanic activity but there is no hot lava to be seen anymore.
To check whether the volcano is active, see the daily report of the Guatemalan government.
Pacaya first erupted approximately 23,000 years ago and has erupted at least 23 times since the Spanish conquest of Guatemala. After being dormant for a century, it erupted violently in 1965 and has been erupting continuously since then, sometimes showering the nearby city of Antigua Guatemala with ash.
This is an active volcano where you can see plenty of lava that cooled to rocks in recent years. The ground is made up of loose volcanic rock and is quite unstable in parts.
Flora and fauna
By far the cheapest option yo visit the volcano is to go on a tour from Antigua which includes transportation, the entrance fee, and the obligatory guide. Such a tour is usually somewhere in the range of US$7 to $15.
There are local buses from Guatemala City. There are no direct local buses from Antigua.
Fees and permits
There is a park entrance fee of Q50 (for foreigners.) And you are required to book a guide which charges Q200 (Q400 for an extended tour.) There is a smaller entrance before you get to the main entrance where you might be able to decrease that amount somewhat. But it is probably much more economic to go on a tour from Antigua.
Walk and take a hiking stick the ground is rocky and in sections it is unstable.
Molten rock, volcanic vents where you can roast marshmallows.
Hiking stick - it'll cost you less than US$1 and should be returned to the local children that sold it to you.
There are shops at the base of the trail.
You can camp here.