First I will address the last section of your question "Is it with payment terms?". A "Loan" is a sum of money which somebody provides with the understanding it will be paid back. That is what "Loan" means. If it were a "gift" then it is not expected to be returned or payed back.
Any loan you receice is going to have payment terms. I think you actually meant repayment terms. First off it needs to be a legal document. If you sign for a loan, which is a signature, then you are agreeing to pay it back. The loan could be written on a napkin and it would be legal if you signed it. Anybody who is in the business of giving loans to people is expecting to make money on that loan. Otherwise why would they loan money to people they do not know or be in business to do so? So, expect to not only pay the amount back you actually received which is called the "Principle amount", expect to pay back an additional amount above what you actually received. This is called "Interest amount", or the amount the lender charges you for them lending it to you. This is the income they receive on the loan. This is where they make their money.
Now, there are vastly differant interest "rates" which is the percentage of the amount you borrowed you will agree to pay in interest for the loan. If you have excellent credit the interest rate could be very low, but don't expect one much lower than 12% on a pesonal loan which does not have collateral. Collateral is something of value you own that you use as a method of the lender getting their money back if you do not pay off the loan. If you stop making payments or never make a payment, they will take the item you placed for collateral for the loan.
However, you are not seeking a loan which requires collateral. Which by the way is how the vast majority of loans are. This "signature loan" you are asking about is most commomly referred as a "personal loan" without collateral. That pushes up the interest rate as well. When you don't have collateral, that makes it a higher risk loan and therfor is assessed a higher interest rate.
There are lenders who are not much higher than loan sharks. Loan sharks are those who give loans to those who despertly need money yet are inelligable for a bank loan or from a lending institution. They charge very high interest rates and can become very ugly if you are late on a payment even once. Be really carefull who you accept a loan from. This really can be very dangerous. Yes there are laws, but you watch the news, there are many violent criminals out in society.
I hope this helps in some way. I really suggest having a wedding within whatever means you currently have and not taking a loan. Especially if you have to resort to a "signature loan" as these are the most likely to be provided by some less than steller members of society. I reassure you there is nothing wrong having a small and inexpensive wedding. I have the means to go with a more lavish wedding but am choosing a much less expensive one. I would rather put that money towards something else than waste it on a one day event, no matter how special. I am not cheap, just practical.
I really do encourage you not to take out a loan in order to have a more expensive wedding than is affordable for you and your fiancee, and/or family budgets. While I most certainly agree a wedding is a special even which should happen once a lifetime, it is silly and irresponsible to go into debt to marry. You are beginning a life with this person and probably plan on starting a family. Why would you want to burden the start of your marriage with debt?
Good luck and much happiness alway in life and your marriage.
Accountant degree, and personal experiance