Theory:

Sexual reproduction is the development of new individuals through the fusion of two types of gametes or sex cells (biparental).
Sexual reproduction is also called amphimixis (amphi means both, mixis means union), syngenesis or amphigony.
 
525px-Sexual_cycle.svg.png
Sexual reproduction involves the fusion of haploid male and female gametes, which occurs at fertilisation resulting in the formation of a diploid zygote
 
The fusion of haploid gametes results in the formation of a diploid zygote which gives rise to offspring. The sexual  mode of reproduction is seen in higher animals.
 
In human beings, the process is sexual reproduction, which involves both male and female sexes. The new individual develops from the fusion cell called a zygote. Human reproduction involves separate and complex male and female reproductive systems. In this chapter, we will study human reproduction in detail. 
Types of sexual reproduction:
a. Syngamy:
 
Fusion of two haploid gametes resulting in the formation of a diploid zygote. Thus, syngamy refers to the process of fertilisation.
 
b. Conjugation:
 
Two organisms come together in a temporary fusion where the male and the female gametes exchange through a temporary cytoplasmic bridge. This is observed in unicellular organisms, such as bacteria and protozoa.
 
Bacterial_Conjugation_en.png
Conjugation in Bacteria
 
Characteristics of Sexual reproduction:
 
1. It involves two parents, i.e., biparental.
 
2. Gametes are always produced.
 
3. The process of fertilisation occurs.
 
4. Mitosis and meiosis are involved in sexual reproduction.
 
5. Variations are present due to the combination or mixing of genes during crossing over.
 
6. Daughter cells are genetically different from the parents.
Reference:
https://commons.wikimedia.org/wiki/File:Sexual_cycle.svg
https://upload.wikimedia.org/wikipedia/commons/0/0a/Bacterial_Conjugation_en.png