Being married is a commitment to build a life together. People that successfully find the right partner are often married for many decades. When their partner passes away, it can throw their entire world into confusion. Many take at least a year to mourn the passing of their partner. After that, they face a life alone unless they find someone new. This is often difficult when people have been married for a long time.
Friends and family will often encourage a person to begin dating again. After spending years with a partner they know, this is difficult for many. They need to find someone that understands their loss and can cope with their complex feelings. Their hope is often that they will be lucky enough to find another partner. This is not a person to replace their previous spouse, but another person they can continue to build their life with over time.