Theory:

Before studying the experiments of Mendel, it is better to know the below terminologies and symbols related to the topic of genetics.
Chromosome, DNA, and gene: 
DNA:
  
"DNA" is a molecule that carries and transmits hereditary information or genetic instructions from parents to offspring.
 
800px-Eukaryote_DNA-en.svg.png
Eukaryotic DNA
 
Gene:
 
The basic physical and functional unit of heredity is the gene. Genes are made up of  DNA.
 
Gene, DNA and chromosome.jpg
Chromosome, DNA, and gene
Allele, trait, and character:
A video explaining the alleles and traits
 
Alleles:
 
Alleles can be homozygous or heterozygous, that is, be in the same or different state.
 
shutterstock1996270916.png
Types of chromosome alleles
 
Allelic genes:
 
Allelic genes are different states of a single gene.
 
Alleles_on_gene (1).jpg
Alleles on gene
 
Character:
 
Character is a distinguishing feature of an individual, such as stem height.
 
Trait:
 
A trait is an inherited characteristic and its detectable variants, such as tallness or dwarfism.
 
Mendels_peas.png
Characteristics of pea plants
 
Allelic traits:
 
Alternative (allelic) traits are contrasting, mutually exclusive traits (white - violet, tall- dwarf).
 
800px-Mendel_pea_traits.svg.png
Alternative traits of pea plant
Dominant and recessive traits:
A video explaining dominant and recessive alleles
 
Dominance:
 
Dominance is the suppression of one alternative feature by another.
 
Dominant trait:
 
A dominant trait is a trait that suppresses the development of another alternative trait.
 
Recessive trait:
 
A recessive trait is a suppressed trait.
 
Dominant allele:
 
The dominant allele is a pair of alleles that can express themselves, whether homozygous or heterozygous. For example, the Red gene (\(V\)) predominates in flower colour over the White gene (\(v\)).
 
800px-Dominant-recessive_inheritance_-_flowers_of_pea_plants.png
Dominant-recessive inheritance - flowers of pea plants
 
The recessive factor of allele:
 
In a heterozygote, the factor of an allelic pair won't express its effect in the presence of its contrasting gene. For example, the '\(a\)' allele in the hybrid pea plant \(Aa\). The recessive factor is only expressed in homozygous states, for example, \(aa\) in pea plants.
 
2924_Mendelian_Pea_Plant_Cross.jpg
Monohybrid cross  
Reference:
https://commons.wikimedia.org/wiki/File:Eukaryote_DNA-en.svg
https://commons.wikimedia.org/wiki/File:Chromosome-DNA-gene_copy.jpg
https://en.wikipedia.org/wiki/File:Alleles_on_gene.jpg
https://commons.wikimedia.org/wiki/File:Mendels_peas.png
https://commons.wikimedia.org/wiki/File:Mendel_pea_traits.svg
https://en.m.wikipedia.org/wiki/File:Dominant-recessive_inheritance_-_flowers_of_pea_plants.png
https://upload.wikimedia.org/wikipedia/commons/thumb/4/4e/2924_Mendelian_Pea_Plant_Cross.jpg/512px-2924_Mendelian_Pea_Plant_Cross.jpg