回复：Depends on your years of service

How many years of service do you have with the company? Normal severance pay is 2 weeks of pay per year of service. Since they are asking you to resign (not that they terminate you - it's a big difference).
When you look for next job, you can say one of the following reasons -
1) Career aspiration - your career interest and current job does not match
2) Personal reasons - family needs - e.g., sick relatives needs you to take care of, etc..
3) Cultural fit - I would use this more carefully - the company culture is not the right fit for you - for example, you like to work in more professional/corporate setting, or you like more fast paced challenging work, or you like job to have travel opportunity, etc.
4) Management style - if you plan to use your current company as reference, you may want to reconsider this.