When I was a baby,
you would hold me in your arms.
I felt the love and tenderness,
keeping me safe from harm.
There are two characters in the poem: the speaker and her special hero.
The speaker and her special hero
The poem starts with the speaker declaring how her special hero would hold her in his arms when she was a baby. Hence, it is understood that the special hero had known the speaker since she was an infant. Besides, we could also see that he was way older than her as he could (or rather, allowed to) hold a baby.
The special hero holding the speaker in his arms

Speaking of the special hero, the speaker recollects how she received all the love and care from him; he loved the speaker very dearly. Furthermore, the speaker had felt safe in his arms. Hence, the speaker thinks that the special hero had protected her from dangers of any kind.
The speaker had received love and protection from her special hero

From the above lines, we could see that the speaker feels love, trust, and gratitude towards her special hero.
The speaker feels love, trust, and gratitude
Meanings of difficult words:
TendernessA feeling of concern, gentle affection, or warmth
HeroA person who is admired for their courage, outstanding achievements, or noble qualities; someone who you admire very much
State Council of Educational Research and Training (2019). Term-3 English Standard-8. Special Hero - Christina M Kerschen (pp. 104). Published by the Tamil Nadu Textbook and Educational Services Corporation.