It's a brilliant game, one of the most enjoyable I have played in a long time.
As a conquistador, the story involves exploration (of the new world). The mechanic for this is similar to early Final Fantasy games, in particular FFVII. In the exploration facet, you can collect herbs, treasure and hunt boar as well as other resources with which you can create tools to help in battle. These resources can also be used in a barter system at settlements. New locations can be found in which you can meet new settlements and peoples.
Meeting people is fun as the game provides a multiple choice story driven dynamic. Your choices, how you interact with the natives, determines your fate and how the story evolves. I was really happy with the choice as it involves you much more in the story and really allows you to play how you like. Diplomacy really is an element in the game in terms of which factions you want to eventually align yourself with (if you want to at all).
As well as multiple choice in dealing with other tribes etc. you must also manage your own crew! You choose your troops at the outset and this is also well done. Each person is given a backstory, general stats and three determining personality attributes i.e. Courageous, Open-Minded, Greedy. The characters all have morale which is affected by your choices in the game - greedy followers would gain morale from stealing from someone for instance while others may lose morale from that. Therefore your relations with the natives will also have an effect, be it positive or negative, on your troops.
As mentioned, you harvest herbs, find treasure and hunt boar in the exploration mode but your troops will need to be carefully selected to manage your resources. Doctors and certain other characters can create medicine from herbs while your hunters can preserve meat. You can also 'tinker' to improve elements such as rate of travel or items whcih will help in battle. Characters can be levelled as you like however. So, there is a lot of mini management involved in the game outside of exploration or battle - one must be strategic. If you make bad strategic decisions the game can be very unforgiving, even on a normal difficulty setting.
Finally, battle! Having explained other elements at some length, I will be brief here - it is essentially turn based strategy. If you have played and enjoyed The Banner Saga or X-Com: Enemy Unknown, you will enjoy this. Fundamentally the mechanic is the same though it is very well done.
I loved this game - 9/10.
Very much hope the developers have a follow up to this in the near future. The system would allow for any theme or universe to be applied - Medieval Europe, Zombie Apocalypse(!), Classical Era (Romans) etc. though I understand the most likely follow up will involve Vikings. It seems the developers want to keep with a 'Expedition' (i.e. coloniser) theme so Zombies are probably out!